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Which is the “best” PE-CE routing protocol?

A comment to my post “Video:Small remote site using BGP as PE-CE routing protocol” has made me think very hard about the PE-CE routing protocol selection. Justin was right: although it’s best for the Service Provider to try to push BGP as far out as possible, it might make customer’s life more complex in some scenarios. I’ve decided to write an article about these PE-CE routing protocol issues, but as I’ve started writing it, it dawned on me: this is not a technical issue, but a business one. You can find my reasoning in the “Choosing customer MPLS VPN routing protocols” article published by

The list of all articles I wrote for SearchTelecom is available in the CT3 wiki.


  1. Ivan,
    in my case BGP wins indeed as the most balanced choice, however we are also in a semi-provider position.
    What comes out in technical aspect is the trend to use BGP almost as an IGP protocol and completely outside of the Internet, thus the choice of AS numbers is becoming a tricky one. For example, there may be a global enterprise using multiple MPLS carriers in different regions as well as using multitenant LAN services (e.g. airports, universities..) that happen to use MPLS as well. Each one of the 'providers' will likely have its own AS numbering policy, with public or private AS's in use. In this situation it is possible to get into the situation of duplicate private AS numbers used. To prevent this, the enterprise should devise its own AS policy and perhaps use a form of AS hiding, or AS 'NAT' like translation, or perhaps just cleaning the path from private AS numbers. Certain IOS features are there to do this, but some are perhaps too strict (remove private AS) because it probably assumes that BGP is used towards the Internet only, and this is not the case any more. Surely, one day we could use extended AS range, but one should have a clear policy there as well.
    There is also not so consistent behavior from provider side in carrying various communities, items like SOO.
    So, BGP might be good choice, with perhaps some modifications to be acceptable and usable in enterprises.
  2. I think it depends on what protocol the customer is using as IGP.. If customer is using EIGRP, the customer is happy when the service provider can support PE-CE EIGRP. If customer is using OSPF , he is happy when service provider can support PE-CE OSPF.. Apparently PE-CE BGP is convenient for service provider.
  3. We exclusively use BGP.

    We opt not to use OSPF/IS-IS despite default
    convergence times "out of the box" (i.e untweaked) being faster and customer familiarity being better, simply because both these protocols rely on repeated SPF runs with customer linkstate churn which we find does not scale in our environment.

    We use BGP and for vpns, a single private AS number which we re-write to our own using the as-override feature and assigning SoO values to sites. We find this scales quite well and we can assign these alongside RD/RT values.
  4. Why should a customer run BGP as routing protocol between the PE and the CE if they are not multihomed?
    Sure BGP is more suitable then an igp for handling large numer of routes , but with proper network design and summarization an igp can work just as well.
    Can anyone tell me a valid technical reason for not running an igp between the PE and CE?
  5. I agree with you Ivan that the provider should be pushing for BGP whenever possible. I built the case from both the provider's and the customer's perspective in the following post, have a look at
  6. @Ovidiu: BGP's function as a PE-CE routing protocol is significantly different from its role as an Internet routing protocol. Your mentions of multi-homing and large number of routes points to this thinking.
    Major reasons why SPs use BGP as a PE-CE is 1) its easier to extend already running BGP in the core to the customer edge 2) most importantly BGP gives you a rich feature set in terms of policies which is a major advantage for traffic path selection, optimization and the likes
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